﻿
$(window).load(function () {

    var theWindow = $(window),
        $bg = $("#bg"),
        aspectRatio = $bg.width() / $bg.height();

    function resizeBg() {

        if ((theWindow.width() / theWindow.height()) < aspectRatio) {
            $bg
                .removeClass()
                .addClass('bgheight');
        } else {
            $bg
                .removeClass()
                .addClass('bgwidth');
        }
    }
    theWindow.resize(resizeBg).trigger("resize");
});